The development of an in vitro model for electrode testing that provides investigators with a cost-effective tool for assessing the long-term electrochemical function of chronically implanted electrodes and reduces the number of animals used in electrode testing is proposed. The focus is on electrodes for neural recording, functional electrical stimulation (FES), and chemical sensing in the central nervous system (CNS) and periphery. Current limitations of in vitro media used for electrode testing include non- physiological buffer, inappropriately high rates of mass transport to electrodes, and inaccurate representation of electrolyte and biomolecule composition. The proposed in vitro model will address these limitations by accurately reflecting the composition and transport properties of the electrode environment as it impacts the electrochemical function of the electrode. In Phase I, the model will be developed and challenged using four examples in which differences between in vivo and in vitro electrode performance have been observed. The model would be expanded in Phase II to include living cells and validated by comparison with electrodes tested in vivo in the CNS and the periphery. PROPOSED COMMERCIAL APPLICATIONS: The commercial product is a laboratory apparatus for long-term electrode testing. The apparatus would contain a suite of test cells and associated test- electrodes and electronics for automated characterization of electrode performance. EIC Laboratories would seek revenue through the manufacture and sale of such equipment or by providing electrode testing services.